Homogenisation device, heat exchanger assembly and method of homogenising a temperature distribution in a fluid stream

ABSTRACT

A homogenisation device which is in particular suitable to homogenise a temperature distribution in a fluid stream exiting a heat exchanger comprises a body with a fluid flow passage extending there through. The homogenisation device further includes a flow control device which is disposed in the fluid flow passage and which is configured to induce a swirl in an outer layer of a fluid stream flowing through the fluid flow passage, while the flow characteristics of a core layer of the fluid stream remain substantially unaffected by the flow control device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is entitled to and claims the benefit of European Application No. 12 176 836.0 filed Jul. 18, 2012 and U.S. Provisional Application No. 61/672,782, filed Jul. 18, 2012, the disclosures of each of which, including the specification, claims, drawings and abstract, are incorporated herein by reference in their entirety.

FIELD

The invention relates to a homogenisation device, a heat exchanger assembly comprising a homogenisation device and a method of homogenising a temperature distribution in a fluid stream.

BACKGROUND

A fluid stream exiting a heat exchanger typically exhibits a temperature gradient across an exit face of the heat exchanger which might affect the accuracy of sensoric temperature measurements downstream of the heat exchanger. Further, the temperature gradient across the exit face of the heat exchanger might impede a partitioning of a main fluid stream exiting the heat exchanger into two or more partial fluid streams having substantially the same temperature.

SUMMARY

The invention is directed at the object of providing a homogenisation device which allows a fast and reliable homogenisation of the temperature distribution in a fluid stream exiting a heat exchanger across an exit face of the heat exchanger without causing excessive pressure losses in the fluid stream. Further, the invention is directed at the object of providing a heat exchanger assembly comprising a homogenisation device of this kind. Finally, the invention is directed at the object of providing a method which allows a fast and reliable homogenisation of the temperature distribution in a fluid stream exiting a heat exchanger across an exit face of the heat exchanger without causing excessive pressure losses in the fluid stream.

These objects are achieved by a homogenisation device having features of attached claims, a heat exchanger assembly having features of attached claims and a method of homogenising a temperature distribution in a fluid stream, the method having features of attached claims.

The homogenisation device according to the invention comprises a body with a fluid flow passage extending therethrough. The body may, for example, at least partially be formed by a header of a heat exchanger, in particular a heat exchanger header which is disposed in the region of an exit of the heat exchanger. Alternatively, the body, however, at least partially may also be formed by a tube extending downstream of a heat exchanger exit. It is, however, also conceivable that the body comprises a first portion which is formed by a header of a heat exchanger and a second portion which is formed by a tube extending downstream of the heat exchanger.

The homogenisation device further comprises a flow control device which is disposed in the fluid flow passage. The flow control device is configured to induce a swirl in an outer layer of a fluid stream flowing through the fluid flow passage, while the flow characteristics of a core layer of the fluid stream remain substantially unaffected by the flow control device. The flow control device does not have to be configured so as to not affect the flow characteristics of the fluid stream core layer at all. Instead, it is, of course, conceivable that the flow control device, for example when the fluid stream passes a downstream region of the flow control device, does influence the fluid stream core layer. In the homogenisation device according to the invention the flow control device, however, is configured to induce a swirl in the outer layer of the fluid stream, while simultaneously, at least for a certain period of time and/or at least along a certain length of the fluid flow passage, the flow characteristics of the fluid stream core layer remain unaffected by the flow control device.

In the homogenisation device according to the invention, the flow control device induces a rotational motion of the outer layer of the fluid stream relative to the core layer of the fluid stream. The flow control device thus is particularly effective to homogenise the temperature distribution in a fluid stream exhibiting a temperature gradient across its cross section, i.e. a temperature gradient in a direction substantially perpendicular to the direction of flow of the fluid stream, since the regions of the fluid stream exhibiting the largest temperature differences, by the rotational motion of the outer layer of the fluid stream relative to the core layer of the fluid stream, are brought into close contact with each other. Compared to the temperature differences present in the outer layer of the fluid stream, the temperature differences in the core layer of the fluid are relatively low. Hence, the fact that the flow control device, at least for a certain period of time and/or at least along a certain length of the fluid flow passage, does not substantially influence the flow characteristics of the fluid stream core layer does not substantially impair the homogenisation effect of the flow control device. Instead, the configuration of the flow control device ensures that the pressure losses in the fluid stream caused by the homogenisation device are limited.

The homogenisation device according to the invention thus allows a fast and reliable homogenisation of the temperature distribution in a fluid stream exhibiting a temperature gradient in a direction substantially perpendicular to the direction of flow of the fluid stream and hence is particularly suitable to homogenise a fluid stream exiting a heat exchanger. Simultaneously, the pressure losses in the fluid stream caused by the homogenisation device are particularly low. When the homogenisation device according to the invention is used to homogenise the temperature distribution in a fluid stream exiting a heat exchanger, the accuracy and reliability of sensoric measurements of the temperature of the fluid stream downstream of the heat exchanger can be improved. Further, in case the fluid stream, downstream of the heat exchanger, should be partitioned into two or more partial fluid streams, the homogenisation device ensures that the partial fluid streams have substantially the same temperature.

The flow control device preferably is disposed in the region of an inner wall of the fluid flow passage. For example, the flow control device may be attached to the inner wall of the fluid flow passage or be formed integral with the inner wall of the fluid flow passage. Further, the flow control device preferably is a static device, which does not comprise moveable elements. A static flow control device does not require the presence of an external energy source for driving the flow control device. Instead, the flow control device allows affecting the flow characteristics of the fluid stream flowing through the fluid flow passage, for example so as to homogenise a temperature distribution in the fluid stream, wherein the energy input required for affecting the flow characteristics of the fluid stream is taken from the fluid stream itself, resulting in a pressure decrease in the fluid stream. However, as discussed above, in the homogenisation device according to the invention, due to the configuration of the flow control device, the pressure losses in the fluid stream caused by the homogenisation device are limited

In a preferred embodiment of the homogenisation device according to the invention the flow control device is configured to cause the outer layer of the fluid stream to follow a coil-shaped fluid flow path along an inner wall of the fluid flow passage. By forcing the outer layer of the fluid stream to follow a coil-shaped fluid flow path, the effective length of the fluid flow path along which homogenisation of the temperature distribution in the fluid stream can be affected is increased. Hence, the homogenisation effect of the homogenisation device is enhanced without it being necessary to increase the required installations space of the homogenisation device.

The flow control device may further be configured to induce coherent eddies in a buffer layer between the outer layer and the core layer of the fluid stream. For example, the configuration of the flow control device may cause coherent eddies to develop in a buffer layer between the outer layer and the core layer of the fluid stream after the period of time during which a swirl is induced in the outer layer of the fluid stream while the flow characteristics of the fluid stream core layer are not affected has passed or after the fluid stream has passed the length of the fluid flow passage along which a swirl is induced in the outer layer of the fluid stream while the flow characteristics of the fluid stream core layer are not affected.

Coherent eddies in a buffer layer between the outer layer and the core layer of the fluid stream, for example, may be induced by a flow control device which is configured to cause pressure differences in the fluid stream, specifically in a downstream region of the flow control device. Coherent eddies in the buffer layer between the outer layer and the core layer of the fluid stream, however, may also be induced when the flow control device causes the outer layer of the flow stream to follow a coil-shaped fluid flow path, whereas the core layer still follows a fluid flow path extending substantially along a longitudinal axis of the fluid flow passage or an angular speed of the swirl induced in the outer layer of the fluid stream is larger than an angular speed of a rotational motion of the core layer which may, for example, be the case in a downstream region of the flow control device. In this case, the relative movement between the core layer and the outer layer induces an additional swirl in the buffer layer between the outer layer and the core layer and hence the development of coherent eddies in the buffer layer between the outer layer and the core layer. The development of coherent eddies in the buffer layer between the outer layer and the core layer of the fluid stream further improves the homogenisation effect of the homogenisation device. Preferably a diameter of the eddies reaches half the size of the diameter of the fluid flow passage resulting in an optimized homogenisation effect of the homogenisation device.

The fluid flow passage may comprise a first portion having a first flow section and a second portion having a second flow section which is smaller than the first flow cross section. For example, the first portion of the fluid flow passed may be defined by a header of a heat exchanger and the second portion of the fluid flow passage may be defined by a tube extending downstream of a heat exchanger.

The flow control device of the homogenisation device according to the invention may comprise at least one flow control blade extending from the inner wall of the fluid flow passage into the fluid flow passage. The flow control blade may be attached to the inner wall of the fluid flow passage or may be formed integral with the inner wall of the fluid flow passage. Preferably, an inner edge region of the at least one flow control blade is arranged at a predetermined distance from a central axis of the fluid flow passage. This design of the flow control blade ensures that the core layer of the fluid stream flowing through the fluid flow passage, at least for a certain period of time and/or at least along a certain length of the fluid flow passage, remains substantially unaffected by the flow control device although the flow control device induces a swirl in the outer layer of the fluid stream. The flow control device may also comprise a plurality of flow control blades, for example four flow control blades, which are distributed along a circumference of the fluid flow passage.

The at least one flow control blade of the flow control device may be inclined relative to the inner wall of the fluid flow passage. Specifically, an angle defined between a first main surface of the flow control blade and the inner wall of the fluid flow passage may be smaller than 90° and an angle defined between a second main surface of the flow control blade and the inner wall of the fluid flow passage may be greater than 90°. The main surfaces of the flow control blade may extend substantially parallel to a longitudinal axis of the fluid flow passage, i.e. substantially parallel to a direction of flow of the fluid stream flowing through the fluid flow passage upstream of the flow control device. A flow control device comprising at least one inclined flow control blade is adapted to induce a swirl, i.e. a rotational motion in a layer of the fluid stream which is affected by the flow control device, such that the outer layer of the fluid stream follows a coil-shaped fluid flow path along the inner wall of the fluid flow passage.

Alternatively or additionally thereto, the at least one flow control blade of the flow control device may be designed such that one of the main surfaces of the flow control blade is provided with a concave curvature. Preferably, the flow control blade is designed such that one of its main surfaces is provided with a concave curvature, whereas the other one of its main surfaces exhibits a convex curvature. A curved flow control blade assists in the development of a swirl in a layer of the fluid stream affected by the flow control device.

In the region of a downstream end of the flow control device, the outer layer of the fluid stream increasingly interacts with the core layer causing the formation of eddies in the buffer layer between the outer layer and the core layer. Further, due to the above described design of the at least one flow control blade, pressure differences between the outer layer and the core layer of the fluid stream occur, in particular downstream of the flow control device, which assists in the development of coherent eddies in the buffer layer between the outer layer and the core layer of the fluid stream.

In case the fluid flow passage comprises a first and a second portion, the at least one flow control blade of the flow control device may comprise a first portion disposed in the first portion of the fluid flow passage and a second portion disposed in the second portion of the fluid flow passage. Preferably, the design of the first and the second portion of the flow control blade is adapted to the flow cross section of the first and the second portion of the fluid flow passage. Specifically, the flow control blade preferably is designed such that an inner edge region of the first portion of the flow control blade and inner edge region of the second portion of the flow control blade are arranged at a substantially constant predetermined distance from the central axis of the fluid flow passage. This design of the flow control blade ensures that the core layer of the fluid stream flowing through the fluid passage remains substantially unaffected by the flow control device although the flow cross section of the second portion of the fluid flow passage is smaller than the flow cross section of the first portion of the fluid flow passage.

The flow control device of the homogenisation device according to the invention may comprise a first coil-shaped groove provided in the region of the inner wall of the fluid flow passage. The groove may be formed integral with the inner wall of the fluid flow passage or may be defined by a groove shaped component attached to the inner wall of the fluid flow passage. A coil-shaped groove formed in the inner wall of the fluid flow passage induces a swirl, i.e. a rotational motion in the outer layer of the fluid stream flowing through the fluid flow passage, whereas a core layer of the fluid stream, at least for a certain period of time and/or at least along a certain length of the fluid flow passage, remains substantially unaffected. Further, the outer layer of the fluid stream, upon flowing through the groove, follows a coil-shaped fluid flow path along the inner wall of the fluid flow passage. In the region of a downstream end of the groove, the outer layer increasingly interacts with the core layer causing the formation of eddies in the buffer layer between the outer layer and the core layer.

The flow control device may further comprise a second coil-shaped groove provided in the region of the inner wall of the fluid flow passage such that alternately a winding of the first coil-shaped groove and a winding of the second coil-shaped groove are provided in the region of the inner wall of the fluid flow passage. Providing the flow control device with two grooves allows to further increase the length of the fluid flow path for the outer layer of the fluid stream and hence to enhance the homogenisation effect of the flow control device. An upstream end of the first coil-shaped groove may be disposed in a first region of the fluid flow passage which is adapted to be flown through with fluid having a first temperature and an upstream end of the second coil-shaped groove may be disposed in a second region of the fluid flow passage which is adapted to be flown through with fluid having a second temperature. This design of the grooves ensures that the fluid having a first temperature is brought into close contact with the fluid having a second temperature and hence the temperature distribution in the fluid stream is homogenised.

A flow control device comprising at least one coil-shaped groove preferably is disposed in the second portion of the fluid flow passage. In particular, the coil-shaped groove may be disposed in the region of an inner wall of a tube extending downstream of a heat exchanger and having a circular cross section.

The flow control device of the homogenisation device according to the invention may comprise either at least one flow control blade extending from the inner wall of the fluid flow passage or at least one coil-shaped groove provided in the region of the inner wall of the fluid flow passage. It is, however, also conceivable that the flow control device of the homogenisation device is provided with both, at least one flow control blade extending from the inner wall of the fluid flow passage and at least one coil-shaped groove provided in the region of the inner wall of the fluid flow passage. For example, at least one flow control blade of the flow control device may at least partially be disposed in a first portion of the fluid flow passage, and at least one coil-shaped groove of the flow control device may be formed in the inner wall of a second portion of the fluid flow passage.

A heat exchanger assembly according to the invention comprises at least one heat exchanger and a homogenisation device as described above. The homogenisation device is disposed at an exit of the heat exchanger and serves to homogenise the temperature distribution in a fluid stream exiting the heat exchanger. The homogenisation device may at least partially be integrated into the heat exchanger. For example, the flow control device of the homogenisation device may at least partially be disposed in a header of the exchanger.

In a method, according to the invention, of homogenising a temperature distribution in a fluid stream a fluid stream is directed through a fluid passage extending through a body. Further, a swirl is induced in an outer layer of the fluid stream flowing through the fluid flow passage by means of a flow control device which is disposed in the fluid flow passage, while, at least for a certain period of time and/or at least along a certain length of the fluid flow passage, the flow characteristics of a core layer of the fluid stream remain unaffected by the flow control device.

Preferably, the outer layer of the fluid stream is caused to follow a coil-shaped fluid flow path along an inner wall of the fluid flow passage.

Preferably, coherent eddies are induced at in a buffer layer between the outer layer and the core layer of the fluid stream.

A homogenisation device, a heat exchanger assembly and/or a method of homogenising a temperature distribution in a fluid stream as described above are particularly suitable for use in an aircraft, in particular for homogenising the temperature distribution in a fluid stream exiting a heat exchanger installed on board the aircraft.

BRIEF DESCRIPTION OF DRAWINGS

Preferred embodiments of the invention now are described in more detail with reference to the appended schematic drawings, wherein

FIG. 1 shows the temperature distribution in a fluid stream exiting a heat exchanger installed on board an aircraft,

FIG. 2 shows a three-dimensional view of a first embodiment of a homogenisation device for homogenising the temperature distribution in a fluid stream exiting a heat exchanger,

FIGS. 3A and 3B show the flow characteristics induced in a fluid stream by the homogenisation device according to FIG. 2,

FIG. 4 shows a first three-dimensional view of a second embodiment of a homogenisation device for homogenising the temperature distribution in a fluid stream exiting a heat exchanger,

FIG. 5 shows a second three-dimensional view of the second embodiment of a homogenisation device for homogenising the temperature distribution in a fluid stream exiting a heat exchanger according to FIG. 4,

FIGS. 6A and 6B show the flow characteristics induced in a fluid stream by the homogenisation device according to FIGS. 4 and 5, and

FIG. 7 shows the influence of the homogenisation devices according to FIGS. 2, 4 and 5 on the temperature distribution in a fluid stream exiting a heat exchanger.

DETAILED DESCRIPTION

FIG. 1 shows the temperature distribution in a fluid stream exiting a heat exchanger installed on board an aircraft. As becomes apparent from FIG. 1, the fluid stream exhibits a temperature gradient across an exit face of the heat exchanger, wherein this temperature gradient is substantially maintained when the fluid stream exits a header of the heat exchanger having a first flow cross section and enters a tube extending downstream of the heat exchanger and having a second flow cross section smaller than the first flow cross section of the heat exchanger header. In the fluid stream, cold fluid prevails in a lower portion of the heat exchanger header and a lower portion of the tube extending downstream of the heat exchanger. In contrast thereto, warm fluid prevails in an upper portion of the heat exchanger header and the tube extending downstream of the heat exchanger. A central region of the fluid stream exhibits a medium temperature. Thus, the fluid stream exiting the heat exchanger exhibits a temperature gradient across its cross section, i.e. in a direction substantially perpendicular to the direction of flow F of the fluid stream.

To homogenise the temperature distribution in a fluid stream exiting a heat exchanger a homogenisation device 10 as depicted in FIG. 2 may be employed. The homogenisation device 10 comprises a body 12 with fluid flow passage 14 extending therethrough. The body 12 comprises a header 16 of a heat exchanger, in particular a header 16 arranged at exit of the heat exchanger. The body 12 further comprises a tube 18 having a circular cross section and extending downstream of the heat exchanger header 16. A direction of flow of the fluid stream exiting the heat exchanger and flowing through the fluid flow passage 14 in FIG. 2, like in FIG. 1, is indicated by the arrow F.

The header 16 of the heat exchanger has a flow cross section that is larger than a flow cross section of the tube 18. Thus, the fluid flow passage 14 extending through the body 12 comprises a first portion 14 a which is defined by the header 16 and has a first flow cross section. Further, the fluid flow passage 14 comprises a second portion 14 b which is defined by the tube 18 extending downstream of the heat exchanger header 16 and which has a second flow cross section smaller than the first flow cross section of the first portion 14 a of the fluid flow passage 14.

The homogenisation device 10 further comprises a flow control device 20 which is disposed in the region of an inner wall 22 of the fluid flow passage 14. In the embodiment of a homogenisation device 10 according to FIG. 2 the flow control device 20 comprises four flow control blades 24 extending from the inner wall 22 of the fluid flow passage 14. The flow control blades 24 are distributed along a circumference of the fluid flow passage 14 and are inclined relative to the inner wall 22 of the fluid flow passage 14 such that an angle α defined by a first main surface 26 of the flow control blades 24 and the inner wall 22 of the fluid flow passage 14 is smaller than 90° and such that an angle β defined between a second main surface 28 of the flow control blades 24 and the inner wall 22 of the fluid flow passage 14 is greater than 90°. Further, the flow control blades 24 are designed such that their first main surface 26 is provided with convex curvature, whereas their second main surface 28 is provided with a concave curvature.

A first upstream portion of the flow control blades 24 is disposed within the first portion 14 a of the fluid flow passage 14, i.e. extends from an inner wall of the header 16. A second downstream portion of the flow control blades 24 is arranged in the second portion 14 b of the fluid flow passage 14, i.e. extends from an inner wall of the tube 18. An inner edge region 30 of the flow control blades 24, however, along the entire extension of the flow control blades 24 in the direction of flow F of the fluid stream flowing through the fluid flow passage 14, is arranged at a predetermined distance from a central axis A of the fluid flow passage 14.

The effect of the flow control device 20 on the flow characteristics of a fluid stream flowing through the fluid flow passage 14 is depicted in FIG. 3. First, the flow control blades 24 of the flow control device 20 induce a swirl S in an outer layer 32 of the fluid stream flowing through the fluid flow passage 14, i.e. a rotational motion of the outer layer 24 of the fluid stream relative to a core layer 34 of the fluid stream, see FIG. 3 a. Due to the rotational motion of the outer layer 32 of the fluid stream regions of the fluid stream having a high temperature are brought into close contact with regions of the fluid stream having a low temperature. As a result, the temperature distribution across the cross section of the fluid stream as depicted in FIG. 1 is significantly homogenised. Since the inner edge region 30 of the flow control blades 24 are arranged at a predetermined distance from the central axis A of the fluid flow passage 14, the core layer 34 of the fluid stream, upon passing an upstream portion of the flow control device 20, remains substantially unaffected by the flow control device 20. The core layer 34 in an upstream region of the flow control device 20 thus, in general, has a direction of flow substantially parallel to the central axis A of the fluid flow passage 14. In any case, an angular speed of the swirl S induced in the outer layer 32 of the fluid stream is larger than an angular speed of a rotational motion of the core layer 34 which may, for example, develop when the fluid stream approaches a downstream region of the flow control device 20. As a result, pressure losses in the fluid stream due to the homogenisation action of the flow control device 20 are minimalized.

Due to the shape and arrangement of the flow control blades 24, the outer layer 32 of the fluid stream flowing through the fluid passage 24 is caused to follow a coil-shaped fluid flow path along the inner wall 22 of the fluid flow passage 24. Compared to a fluid flow path extending parallel to the central axis A of the fluid flow passage 14 a coil-shaped fluid flow path along the inner wall 22 of the fluid flow passage 14 is significantly longer without requiring the homogenisation device 10 to have larger dimensions and thus requiring a larger installation space. Nevertheless, homogenisation of the temperature distribution in the fluid stream may take place along the entire length of the coil-shaped fluid flow path such that a very effective homogenisation of the temperature distribution in the fluid stream may be achieved.

Due to the relative motion between the outer layer 32 and the core layer 34 of the fluid stream and due to pressure differences present in a downstream region of the flow control device 20, coherent eddies are induces in a buffer layer I between the outer layer and the core layer of the fluid stream downstream of the flow control device 20, see FIG. 3 b. Hence, downstream of the flow control device 20 also the core layer 34 of the fluid stream is involved in turbulent flow characteristics which further improve the homogenisation effect of the homogenisation device 10.

FIGS. 4 and 5 show a second embodiment of a homogenisation device 10. The homogenisation device 10 according to FIGS. 4 and 5 differs from the arrangement according to FIG. 2 in that the flow control device 10 does no longer comprise flow control blades 24 extending from the inner wall 22 of the fluid flow passage 14, but a first and second coil-shaped groove 36, 38 formed in the inner wall 22 of the fluid flow passage 14. An upstream end of the first groove 36 is disposed in a lower region of the fluid flow passage 14, i.e. in a region of the fluid flow passage 14 which is flown through with fluid having a low temperature. An upstream end of the second groove 38 formed in the inner wall 22 of the fluid flow passage 14, by contrast, is arranged in an upper region of the fluid flow passage 14, i.e. in region of the fluid flow passage 14 which is flown through with fluid having a high temperature.

The grooves 36, 38 formed in the inner wall 22 of the fluid flow passage 14, like the flow control blades 24 of the flow control device 20 in the homogenisation device 10 according to FIG. 2, first induce a swirl S in the outer layer 32 of the fluid stream flowing through the fluid flow passage 14, whereas, upon passing an upstream region of the flow control device 20, the core layer 34 of the fluid stream remains substantially unaffected by the flow control device 20, see FIG. 6 a. Due to the rotational motion of the outer layer 32 relative to the core layer 34 fluid having a low temperature is brought into close contact with fluid having a high temperature resulting in a homogenisation of the temperature distribution in the fluid stream flowing through the fluid flow passage 14. Simultaneously, pressure losses in the fluid stream caused by the flow control device 20 are minimized.

The core layer 34 in an upstream region of the flow control device 20, in general, has a direction of flow substantially parallel to the central axis A of the fluid flow passage 14. In any case, an angular speed of the swirl S induced in the outer layer 32 of the fluid stream is larger than an angular speed of a rotational motion of the core layer 34 which may, for example, develop when the fluid stream approaches a downstream region of the flow control device 20. The outer layer 32 of the fluid stream following a coil-shaped fluid flow path along the inner wall 22 of the fluid flow passage 14 thus acts as a kind of “roller bearing” for the core layer 34, resulting in a rotational motion of the fluid strands defines by the grooves 36, 38 about a central axis of the strands, wherein this rotational motion of the strands is maintained even downstream of the grooves 36, 38. In a downstream region of the flow control device 20 the relative movement between the outer layer 32 and the core layer 34 of the fluid stream induces coherent eddies in a buffer layer I between the outer layer 32 and the core layer 32 of the fluid stream, see FIG. 6 b. In a downstream region of the flow control device 20 thus also the core layer 34 of the fluid stream is involved in the turbulent flow characteristics induced by the flow control device 20. As a result the homogenisation effect of the homogenisation device 10 can further be enhanced.

The effect of the homogenisation devices 10 according to FIGS. 2, 4 and 5 are depicted in FIG. 6. Specifically, FIG. 6 reveals that the temperature distribution in the fluid stream across the cross section of the fluid stream, i.e. in a direction substantially perpendicular to the general direction of flow F of the fluid stream is substantially homogenised.

In the exemplary embodiments of a homogenisation device 10 as described above the flow control device 20 comprises either flow control blades 24 or grooves 36, 38 formed in an inner wall 22 of the fluid flow passage 14. It is, however, also conceivable to provide a flow control device 20 with both, flow control blades 24 and at least one groove 36, 38 provided in the inner wall 22 of the fluid flow passage 14. Further, all features described above with reference to only one exemplary embodiments of the homogenisation device 10 can also be employed in another embodiment of the homogenisation device 10. 

1. Homogenisation device comprising: a body with a fluid flow passage extending there through, and a flow control device which is disposed in the fluid flow passage and which is configured to induce a swirl in an outer layer of a fluid stream flowing through the fluid flow passage, while the flow characteristics of a core layer of the fluid stream remain substantially unaffected by the flow control device.
 2. Homogenisation device according to claim 1, wherein the flow control device is configured to cause the outer layer of the fluid stream flowing through the fluid flow passage to follow a coil-shaped fluid flow path along an inner wall of the fluid flow passage.
 3. Homogenisation device according to claim 1, wherein the flow control device is configured to induce coherent eddies in a buffer layer disposed between the outer layer (and the core layer of the fluid stream.
 4. Homogenisation device according to claim 1, wherein the fluid flow passage comprises a first portion having a first flow cross section and a second portion having a second flow cross section smaller that the first flow cross section.
 5. Homogenisation device according to claim 1, wherein the flow control device comprises at least one flow control blade extending from the inner wall of the fluid flow passage into the fluid flow passage, wherein an inner edge region of the at least one flow control blade preferably is arranged at a predetermined distance from a central axis of the fluid flow passage.
 6. Homogenisation device according to claim 5, wherein the at least one flow control blade is inclined relative to the inner wall of the fluid flow passage such that an angle defined between a first main surface of the flow control blade is smaller than 90° and an angle defined between a second main surface of the flow control blade is greater than 90° and/or the at least one flow control blade is designed such that one of the main surfaces is provided with a concave curvature.
 7. Homogenisation device according to claim 5, wherein the at least one flow control blade comprises a first portion disposed in the first portion of the fluid flow passage and a second portion disposed in the second portion of the fluid flow passage.
 8. Homogenisation device according of claim 1, wherein the flow control device comprises a first coil-shaped groove formed in the region of the inner wall of the fluid flow passage.
 9. Homogenisation device according to claim 8, wherein the flow control device comprises a second coil-shaped groove formed in the region of the inner wall of the fluid flow passage such that alternately a winding of the first coil-shaped groove and a winding of the second coil-shaped groove are formed in the region of the inner wall of the fluid flow passage, wherein an upstream end of the first coil-shaped groove is disposed in a first region of the fluid flow passage which is adapted to be flown through with fluid having a first temperature and an upstream end of the second coil-shaped groove is disposed in a second region of the fluid flow passage which is adapted to be flown through with fluid having a second temperature so as to ensure that the fluid having a first temperature is brought into close contact with the fluid having a second temperature.
 10. Homogenisation device according to claim 8, wherein the flow control device is disposed in the second portion of the fluid flow passage.
 11. Heat exchanger assembly comprising: a heat exchanger, and a homogenisation device according to claim 1, the homogenisation device being disposed at an exit of the heat exchanger.
 12. Method of homogenising a temperature distribution in a fluid stream, the method comprising the steps: directing a fluid stream through a fluid passage extending through a body, and inducing a swirl in an outer layer of the fluid stream flowing through the fluid flow passage by means of a flow control device which is disposed in the fluid flow passage, while the flow characteristics of a core layer of the fluid stream remain substantially unaffected by the flow control device.
 13. Method according to claim 12, wherein the flow control device causes the outer layer of the fluid stream flowing through the fluid flow passage to follow a coil-shaped fluid flow path along an inner wall of the fluid flow passage.
 14. Method according to claim 12, wherein coherent eddies are induced in a buffer layer between the outer layer and the core layer of the fluid stream.
 15. Use of a homogenisation device according to claim 1 in an aircraft.
 16. Use of a heat exchanger assembly according to claim 10 in an aircraft.
 17. Use of a method according to claim 12 in an aircraft. 